Method and system for determining non-uniformity characteristics of a vehicle tire and rim

ABSTRACT

A method and system for a wheel assembly service system are provided. The system includes a rotatable spindle configured to receive a wheel assembly wherein the wheel assembly includes at least a rim and a tire. The system further includes a load device configured to apply a load to the tire during a rotation of the wheel assembly on the spindle, and a controller configured to determine a first force variation vector of the wheel assembly, prompt a user to rotate the tire with respect to the rim, determine a second force variation vector of the wheel assembly with the tire rotated with respect to the rim, and determine a force variation of at least one of the tire and the wheel using the first and second force variation vectors. The system also outputs at least one of the determined force variation vector values.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/478,904 filed Jun. 5, 2009 and now issued U.S.Pat. No. 8,186,215, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/059,846 filed Jun. 9, 2008, the disclosures ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

This invention relates generally to vehicle wheel service systems and,more particularly, to a method and system for determining vehicle wheelrunout and correcting for mismatched wheel assembly runout.

At least some known vehicles experience vibration at road speeds due tonon-uniformity in the vehicle's wheel assemblies. The wheel assemblyincludes a tire coupled to a rim. The non-uniformity may be due toimperfections or damage to the rim and/or tire. The non-uniformity mayinclude a spring rate variation in the tire. The spring rate variationrelates to a tire's stiffness at areas spaced about the circumference ofthe tire. As the stiff area rotates into contact with the road, the tirereacts differently than at other areas of the tire. This differenceproduces a force variation at a rotational speed of the tire, leading toa first harmonic vibration. Force variation is measured while theinflated tire is rolled against an instrumented drum.

Force variation can be measured while the inflated tire is rolledagainst an instrumented drum or roller. The prior art can also remountthe tire at an optimal position relative to the rim during a matchingprocedure to reduce or eliminate force variation as an assembly. Otherprior art can measure unloaded runout using contactless measurement andoptimally position the tire relative to the rim based on runout insteadof force variation. These matching procedures (on systems with orwithout a load roller) require measurement of rim runout. The measuredrim contribution is then subtracted from the measured assembly result,yielding a tire-only contribution to the assembly effect. Rim runout istypically measured with the tire mounted for convenience reasons, butthere are problems associated with measuring runout in this manner. Manyof today's wheels do not provide a proper surface to measure rim runoutwith the tire mounted, and removal of the tire to measure the bare rimdirectly at the bead seats is too labor intensive for many customers. Anadditional problem is that errors can happen with both contact andnon-contact rim runout measurement with the tire mounted because thephysical bead seat is not what is being measured. For example, the beadseats on an aluminum wheel could be machined a the last manufacturingstep, resulting in a surface which does not correlate to any of theexternal rim surfaces accessible by runout measuring devices when thetire is mounted. Another situation can exist where the rim width variesalong different angular locations of the rim as shown by the two extremerim lip positions 160 and 160 a of FIG. 2. The narrower sections squeezethe beads closer together, altering the geometric positioning of thetire carcass and correspondingly the assembly radial force variation.The prior art measures lateral rim runout but only as an audit to checkthe rim, but in the event that tire construction details were to be madeknown to the wheel service system the lateral rim runout could be usedto predict the effect on assembly radial force variation.

The present invention provides a way to determine the contributions ofthe tire and rim individually without measuring rim runout at all,avoiding the aforementioned drawbacks and providing a more accurateresult.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a wheel assembly service system includes a rotatablespindle configured to receive a wheel assembly wherein the wheelassembly includes at least a rim and a tire. The system further includesa load device configured to apply a load to the tire during a rotationof the wheel assembly on the spindle, and a controller configured todetermine a first force variation vector of the wheel assembly, prompt auser to rotate the tire with respect to the rim, determine a secondforce variation vector of the wheel assembly with the tire rotated withrespect to the rim, and determine the force variation component due tothe tire and the component due to the rim.

In another embodiment, a method of determining non-uniformity of a wheelassembly wherein the wheel assembly includes a rim and a tire isprovided. The method includes determining a first force variation vectorof the wheel assembly, rotating the tire with respect to the rim,determining a second force variation vector of the wheel assembly,determining a force variation component due to the tire and thecomponent due to the rim.

In yet another embodiment, a wheel assembly-service system includes aspindle configured to receive a wheel assembly wherein the wheelassembly includes a rim and a tire mounted on the rim. The spindleconfigured to rotate the wheel assembly about a rotational axis of thewheel assembly. The wheel assembly-service system further includes aload device configured to apply a load to the tire, the load simulatinga road force experienced by the wheel assembly in use and a controllercommunicatively coupled to the spindle and the load device. Thecontroller is configured to control a rotation of the spindle and aforce applied to the wheel assembly using the load device. Thecontroller is further configured to determine a first force variationvector of the wheel assembly, prompt a user to rotate the tire withrespect to the rim, determine a second force variation vector of thewheel assembly with the tire rotated with respect to the rim, determinea force variation component due to the tire and the component due to therim.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-7 show exemplary embodiments of the method and system describedherein.

FIG. 1 is schematic diagram of a wheel service system in accordance withan embodiment of the present invention;

FIG. 2 is a cross-sectional view of rim illustrating known runoutmeasurement methods;

FIG. 3 is a schematic side view of a wheel assembly mounted on a spindlein accordance with an embodiment of the present invention;

FIG. 4A is a force vector diagram for an exemplary wheel assembly shownin FIG. 1 that may be used with wheel service system;

FIG. 4B is a force vector diagram for the wheel assembly shown in FIG. 1with the tire rotated 180° with respect to the rim;

FIG. 4C is a force vector diagram for the wheel assembly shown in FIG. 1showing the respective measured vectors;

FIG. 4D is a force vector diagram for the wheel assembly shown in FIG. 1illustrating resolving the component vectors of the measured vectorsshown in FIG. 4C;

FIG. 5 is another screen display illustrating another step of theprocedure that may be used with an exemplary embodiment of the presentinvention;

FIG. 6 is another screen display illustrating another step of theprocedure that may be used with an exemplary embodiment of the presentinvention; and

FIG. 7 is another screen display illustrating another step of theprocedure that may be used with an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description illustrates embodiments of theinvention by way of example and not by way of limitation. It iscontemplated that the invention has general application to determiningnon-uniformity of multiple components of an assembly by measuring aparameter of the assembly in industrial, commercial, and consumerapplications. Non-uniformity may include, but is not limited to, forcevariation and runout.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralelements or steps, unless such exclusion is explicitly recited.Furthermore, references to “one embodiment” of the present invention arenot intended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

FIG. 1 is schematic diagram of a wheel service system 100 in accordancewith an embodiment of the present invention. In one embodiment, wheelservice system 100 comprises a balancer including a rotatable shaft orspindle 102 driven by a drive mechanism (not shown) such as an electricmotor. A shaft encoder 104 is mounted on spindle 102 to provide speedand rotational position information regarding spindle 102. A wheelassembly 106 under test generally comprises a tire 107 coupled to a rim109 and is removably mounted for rotation to spindle 102.

A load roller 108 is positionable adjacent wheel assembly 106. In afirst position 110, load roller 108 is maintained a distance away fromwheel assembly 106. In a second position 112, load roller 108 ismaintained in light contact with wheel assembly 106 such that loadroller 108 contacts an outer peripheral surface 114 of wheel assembly106 but does not apply a substantial force to wheel assembly 106. Asused herein, “light contact” refers to just enough force to enable loadroller 108 to track along surface 114. In a third position 116, loadroller 108 is engages wheel assembly 106 such that a radially inwardforce is applied to surface 114. The magnitude of the force depends onthe position of load roller 108 relative to wheel assembly 106. Loadroller 108 is coupled to a shaft 117 which in turn is coupled to an arm118 configured to pivot about a shaft 120. A sensor 121 detects anamount and direction of rotation of shaft 120. A controller 122 iscommunicatively coupled to an air cylinder or air bag 124. Controller122 includes a memory 123 for storing data and/or a program that isexecutable by controller 122 for implementing the procedures describedherein. Controller 122 directs arm 118 to pivot to place load roller 108into any of various positions described above by actuating air cylinder124. Air pressure to cylinder 124 is variably adjusted by controller122. A sensor 126 provides air pressure feedback that enables preciseload roller forces to be generated.

In another embodiment, wheel service system 100 comprises a tirechanger.

FIG. 2 is a cross-sectional view of rim 109 illustrating known runoutmeasurement methods. In one method of measuring rim runout, an indexroller 150 is manually engaged to a lip 152 on a rim flange 154. Rim 109is rotated slowly while index roller 150 is maintained in engagementwith lip 152. A position indicator (not shown) coupled to index roller150 determines a position of roller 150 to measure a runout of rim 109.Index roller 150 engaging an outside portion of rim 109 can notaccurately measure a lateral lip runout on some wheels, including manymodern wheels. Index roller 150 must be used with tire 107 installed onrim 109. With tire 107 removed, a ball probe 156 is manually positionedin a bead seating area 158 of rim 109. Rim 109 is rotated slowly whileball probe 156 is maintained in engagement with bead seating area 158.Rim width variation occurs when a radially outwardly extending bead wall160 is bent inwardly 160 a towards tire 107. The narrower sectionssqueeze the beads closer to each other, altering the geometricpositioning of the tire carcass and correspondingly the assembly forcevariation. The effect on the assembly force variation also depends onthe construction type of the tire (aspect ratio, size, stiffness, etc.)therefore can be difficult to predict even if a rim runout system canobtain lateral measurements along with the radial measurement.Conversely, using the procedure described herein using a first assemblymeasurement and a second assembly measurement where tire 107 is rotated180° (but can be an angle other than 180° as long as the angle is knownto the wheel service system) with respect to rim 109, the effects of rimwidth variation and any other non-pure radial rim imperfections arenaturally built into the result.

FIG. 3 is a schematic side view of wheel assembly 106 mounted on spindle102 in accordance with an embodiment of the present invention. Wheelassembly 106 includes tire 107 coupled to rim 109. When a radiallyinward force 302 is applied to tire 107 using load roller 108, a forcevariation vector 304, comprising a magnitude value and a phase value,may be determined using sensors 121 and/or 126 (shown in FIG. 1). Theforce vectors are represented by a force vector F_(A) of the entirewheel assembly 106, a force vector F_(T) for the tire contribution toF_(A), and a force vector F_(R) for the rim contribution to F_(A).

FIG. 4A is a force vector diagram 300 for an exemplary wheel assembly106 that may be used with wheel service system 100. FIG. 4B is a forcevector diagram 320 for wheel assembly 106 with tire 107 rotated 180°with respect to rim 109. FIG. 4C is a force vector diagram 340 for wheelassembly 106 showing the respective measured vectors. FIG. 4D is a forcevector diagram 360 for wheel assembly 106 illustrating resolving thecomponent vectors of the measured vectors shown in FIG. 4C. An initialforce vector F_(A1) of wheel assembly 106 is measured using wheelservice system 100. Vector F_(A1) may be displayed on wheel servicesystem 100 depending on a selection by a user. Component vectors ofF_(A1), force vector F_(R), attributable to a “high spot” in the runoutof rim 109 and force vector F_(T), attributable to a “high spot” in therunout of tire 107, are unknown. FIG. 4B illustrates the force vectorsof wheel assembly 106 with tire 107 rotated 180° with respect to rim109. A second force variation vector F_(A2) is then measured. FIG. 4Cillustrates the two measured vectors F_(A1) and F_(A2). FIG. 4Dillustrates determining the component vectors F_(R) and F_(T). From thedetermined components, a prediction of the amount of rotation of tire107 with respect to rim 109 is made to locate the respective “highspots” of tire 107 and rim 109 at positions that are spacedapproximately 180° apart on wheel assembly 106. Although the matchingprocedure is described above using load roller 108 to provide forcevariation measurements to determine runout of wheel assembly 106, alight contact may be applied by load roller 108 or a non-contactmeasurement of runout of wheel assembly 106 may be made using anon-contact sensor (not shown). A “light” load roller or non-contactsystem would base matching on runout, not force variation.

Referring to FIG. 3, to determine force vector F _(R) and force vector F_(T), F _(A1) is measured on system 100.F _(A1)= F _(R)+ F _(T), where F _(T) and F _(R) are unknown.  (1)

Tire 107 is deflated and tire 107 is rotated 180° with respect to rim109. Tire 107 is reinflated and a force vector F _(A2) of wheel assembly106 is measured.F _(A2)= F _(R)− F _(T)  (2)

Because tire 107 is 180° out of phase with respect to its position whenmeasuring F _(A1), F _(T) is negative.

Finding the difference between F _(A1) and F _(A2) yields:F _(A1)= F _(R)+ F _(T)− F _(A2)= F _(R)− F _(T)F _(A1)− F _(A2)=2 F _(T), solving for F _(T) yields

$\overset{\_}{F_{T}} = \frac{\overset{\_}{F_{A\; 1}} - \overset{\_}{F_{A\; 2}}}{2}$

Substituting for F _(T) in equation 1 yields,

${\overset{\_}{F_{A\; 1}} = {\overset{\_}{F_{R}} + \frac{\overset{\_}{F_{A\; 1}} - \overset{\_}{F_{A\; 2}}}{2}}},$solving for F _(R) yields,

$\overset{\_}{F_{R}} = {\frac{\overset{\_}{F_{A\; 1}} - \overset{\_}{F_{A\; 2}}}{2}.}$

With F _(R) and F _(T) being known, they can be matched to provide thelowest possible assembly force variation F _(A).

FIG. 5 is a screen display 500 that may be used with an exemplaryembodiment of the present invention. Screen display 500 may include atitle block 502 to inform the user the procedure currently beingimplemented by system 100. A progress bar 504 informs the user of anestimate the elapsed procedure and an estimate of how much of theprocedure remains before completion. An instruction area 506 includesstep-by-step instructions for the user to implement the procedure, aswell as alerts, cautions, data, and help items that facilitate theprocedure. Screen display 500 also includes one or more graphics panes508, 510, and 512 in the present example. A series of softkeys 514permits the user to make selections and inputs to the program executingthe procedure. Graphics panes 508, 510, and 512 include pictures andgraphics to assist in explaining the procedure to the user as well aspermitting the user to see the progress of the procedure in a graphicalform. Graphic pane 508 illustrates what wheel assembly 106 should looklike to the user when the steps shown in instruction area 506 arecompleted. The user is then prompted to indicate the illustrated stepsare complete by clicking on an appropriate softkey 514. Graphics panes508, 510, and 512 may include a highlight, for example, a highlightedborder 516 indicating that pane is illustrating the active step. In theexemplary screen display 500, instruction area 506 instructs the user to“Mark the tire with a ‘V’ opposite the valve stem as indicated” toprepare for 180° rotation. Instruction area 506 further instructs theuser to “Lower hood to start the RoadForce measurement.”

A further capability of the present invention is to combine imbalancemeasurement with each of the steps of the procedure that measureassembly force variation (or runout if applicable) with the tire mountedat two different angular positions on the rim. The magnitudes locations(vectors) of the rim and tire contributions to the assembly imbalancecan be computed in the same manner as the force variation vectors. Withthis additional information, intelligent decisions can be made for thefinal tire remount position on the rim which weigh predictions of bothimbalance and force variation (or runout if applicable). For example ifthe rim is very round (has little to no runout) and the resultingmatched prediction will have little to no change at any mounted tireposition, then a match rotation could then be considered which willimprove the final imbalance of the assemble to save total weight usagewhen balancing the wheel.

Additionally, the method outlined by the presented invention can beperformed with the wheel assembly mounted on the vehicle under a loaded,lightly loaded, or unloaded condition. The wheel service system in thiscase would provide portable hardware to measure the assembly for the twomeasurement steps which have the tire mounted at two different positionson the rim. The on-car system could also have combined functionality asan on-car balancer, also having the capability of weighing predictionsof both assembly imbalance and assembly runout (or force variation if aloaded system) when computing the optimal tire remount position.

FIG. 6 is another screen display 700 that may be used with an exemplaryembodiment of the present invention. Instruction area 506 providesfurther instructions for rotating the tire 180° and graphics panes 508and 510 illustrate the provided instructions as well as an indication ofroad force FA₁ in a data area 702 of graphics pane 508. In the exemplaryscreen display 700, instruction area 506 instructs the user to “Breakdown the tire and rotate 180° on the rim, aligning mark with valvestem.” Instruction area 506 further instructs the user to “Mountassembly on balancer” and to “Position valve stem at 12:00 and press“Enter Valve Stem.””

FIG. 7 is another screen display 900 that may be used with an exemplaryembodiment of the present invention. Instruction area 506 providesfurther instructions for implementing the procedure. In the exemplaryscreen display 900, instruction area 506 instructs the user to “Rotatethe tire mark indicator to 12:00 and apply mark on the tire.”Instruction area 506 also instructs the user to “Rotate rim markindicator to 12:00 and apply mark on outside of wheel.” Instruction area506 further instructs the user to indicate completion of the step bypressing “OK.” Graphics panes 508 and 510 illustrate the providedinstructions as well as an indication of road force FA₁ in a data area702 of graphics pane 508 and road force FA₂ in a data area 902 ofgraphics pane 510. A determined runout of rim 109 and a road force oftire 107 are illustrated in data areas 904 and 906, respectively. A dataarea 908 of graphics pane 512 illustrates a determined prediction of thetotal road force of wheel assembly 106 when the “high spot” of tire 107and rim 109 are arranged opposite each other. Instruction area 506provides a result of the completed road force verification procedure.

The term controller, as used herein, refers to processors, centralprocessing units, microprocessors, microcontrollers, reduced instructionset circuits (RISC), application specific integrated circuits (ASIC),logic circuits, and any other circuit or processor capable of executingthe functions described herein.

As used herein, the terms “software” and “firmware” are interchangeable,and include any computer program stored in memory 123 for execution byprocessor 122, including RAM memory, ROM memory, EPROM memory, EEPROMmemory, and non-volatile RAM (NVRAM) memory. The above memory types areexemplary only, and are thus not limiting as to the types of memoryusable for storage of a computer program.

As will be appreciated based on the foregoing specification, theabove-described embodiments of the disclosure may be implemented usingcomputer programming or engineering techniques including computersoftware, firmware, hardware or any combination or subset thereof,wherein the technical effect is measuring a road force and/or runout ofa wheel assembly in a first orientation, rotating the tire with respectto the rim and measuring the road force and/or runout of the wheelassembly in the rotated orientation. The processor determines a roadforce vector attributable to the rim and the tire using the measuredroad force and/or runout and determines a predicted road force value forthe orientation where the “high spot” of the rim and the “high spot” ofthe tire are aligned opposing each other. This “high spot's” matching isnot necessarily matching the physical high spots, but rather providing amatch that results in the lowest overall vibration of the matched tireand rim assembly. The processor then compares the predicted value to anallowable value and displays whether the matched tire and rim meets anallowable range. Any such resulting program, having computer-readablecode means, may be embodied or provided within one or morecomputer-readable media, thereby making a computer program product,i.e., an article of manufacture, according to the discussed embodimentsof the disclosure. The computer readable media may be, for example, butis not limited to, a fixed (hard) drive, diskette, optical disk,magnetic tape, semiconductor memory such as read-only memory (ROM),and/or any transmitting/receiving medium such as the Internet or othercommunication network or link. The article of manufacture containing thecomputer code may be made and/or used by executing the code directlyfrom one medium, by copying the code from one medium to another medium,or by transmitting the code over a network.

The above-described embodiments of a method and system of measuringwheel assembly runout and/or road force at two different orientations ofthe tire on the rim provides a cost-effective and reliable means fordetermining the runout and/or road force contribution of the rim and ofthe tire and optionally considering other determined factors such as therim and tire contributions to assembly imbalance. The determined valuesmay be utilized to predict the final road force and/or runout and/orimbalance. As a result, the methods and systems described hereinfacilitate matching a tire to a rim such that the wheel assembly meetsroad force and/or runout specifications in a cost-effective and reliablemanner.

While the disclosure has been described in terms of various specificembodiments, it will be recognized that the disclosure can be practicedwith modification within the spirit and scope of the claims.

What is claimed is:
 1. A tire changer comprising: a rotatable spindleconfigured to receive a wheel assembly, the wheel assembly comprising atleast a rim and a tire; and a controller configured to: determine afirst non-uniformity of the wheel assembly; initiate rotation of thetire with respect to the rim; determine a second non-uniformity of thewheel assembly with the tire rotated with respect to the rim; anddetermine a non-uniformity component associated with the tire utilizingsaid first determined non-uniformity and said second determinednon-uniformity.
 2. A tire changer in accordance with claim 1 whereinsaid controller is further configured to determine a non-uniformitycomponent associated with the rim.
 3. A method of determining forcevariation attributable to a tire in a wheel assembly wherein the tire iscoupled to a rim, the method implemented on a tire changer including acontroller, method comprising: determining a first force variation ofthe wheel assembly while the tire is in a first rotational position withrespect to the rim; rotating the tire with respect to the rim to asecond rotational position with respect to the rim; determining a secondforce variation of the wheel assembly while the tire is in the secondrotational position; and determining, with the controller, a forcevariation component associated with the tire using the determined firstforce variation and the determined second force variation.
 4. A methodof measuring non-uniformity of a wheel assembly in accordance with claim3 further comprising determining a force variation component associatedwith the rim.
 5. A wheel assembly service system comprising: a rotatablespindle configured to receive a wheel assembly, the wheel assemblycomprising at least a rim and a tire; and a controller configured to:determine a first non-uniformity of the wheel assembly; initiaterotation of the tire with respect to the rim; determine a secondnon-uniformity of the wheel assembly with the tire rotated with respectto the rim; and determine a non-uniformity component associated with therim utilizing said first determined non-uniformity and said seconddetermined non-uniformity.
 6. A wheel assembly service system inaccordance with claim 5 wherein said controller is further configured todetermine a non-uniformity component associated with the tire.
 7. Awheel assembly service system in accordance with claim 5, wherein thewheel assembly service system is configured as a tire changer machine.8. A wheel assembly service system in accordance with claim 5, whereinthe wheel assembly service system is configured as a wheel balancermachine.
 9. A method for measuring the non-uniformity of a wheelassembly that includes a tire coupled to a rim, said method implementedwith a wheel assembly service system including a controller, and saidmethod comprising: determining a first non-uniformity of the wheelassembly; rotating the tire with respect to the rim; determining asecond non-uniformity of the wheel assembly with the tire rotated withrespect to the rim; and determining, with the controller, anon-uniformity component associated with the rim utilizing thedetermined first non-uniformity and the determined secondnon-uniformity.
 10. A method in accordance with claim 9 furthercomprising determining a non-uniformity component associated with thetire.
 11. A wheel assembly service system comprising: a rotatablespindle configured to receive a wheel assembly, the wheel assemblyincluding at least a rim and a tire; and a controller configured todetermine a force variation component associated with at least one ofthe rim and the tire without measuring a rim runout; wherein the wheelassembly service system is configured as a tire changer machine.
 12. Thewheel assembly service system of claim 11, wherein the controller isfurther configured to: determine a first force variation of the wheelassembly; and initiate rotation of the tire with respect to the rim. 13.The wheel assembly service system of claim 11, wherein the controller isfurther configured to: determine a second force variation of the wheelassembly with the tire rotated with respect to the rim; and determine aforce variation component associated with at least one the tire and therim utilizing said determined first force variation and said secondforce variation.
 14. A wheel assembly service system in accordance withclaim 11, wherein the wheel assembly service system further includes aload device configured to apply a load to the tire during a rotation ofthe wheel assembly on the spindle.
 15. A wheel assembly service systemcomprising: a rotatable spindle configured to receive a wheel assembly,the wheel assembly including at least a rim and a tire; and a controllerconfigured to, without measuring a rim runout, determine a firstnon-uniformity component associated with the rim and a secondnon-uniformity component associated with the tire.
 16. A wheel assemblyservice system of claim 15, wherein the wheel assembly service system isconfigured as a tire changer machine.
 17. A wheel assembly servicesystem in accordance with claim 15, wherein the wheel assembly servicesystem is configured as a wheel balancer machine.
 18. A wheel assemblyservice system of claim 15, wherein the wheel assembly service systemfurther includes a load device configured to apply a load to the tireduring a rotation of the wheel assembly on the spindle.